There really isn't a lot of information about the Sith Order
. The Sith is a race of aliens that have since died out long before the creation of the Galactic Empire. Members of the Sith Order are darkside users that stumbled upon the Sith [race], and over the years they got their thang on and lived happily ever after. Long story short, hyperspace adventurer, discover Sith planet, Sith attack Old Republic, long wars, yada yada, Sith Wars, yada yada, Darth Bane, and then the Sith Order bide their time.
I don't know how much official
information there is from Darth Bane to Sidious.
You asked for my opinion on the Dark Side, there is no Dark Side! Only the Force.
But seriously, the Dark Side is corrupting. Apprentices overthrow their masters to become Lord of the Sith, and repeat. Heck, even Darth Vader overthrows his master.
Also in the future, it'd help discussions if you were more clear. I find it hard to wrap my mind about what you're saying/asking, but that could just be me. :/